<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>层级</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }
        ul {
            margin: 100px auto;
            list-style: none;
            width: 1000px;
        }
        li {
            width: 190px;
            height: 300px;
            float: left;
            border: 1px solid #B61D1D;
            margin-left: -1px;
            cursor: pointer;
            position: relative;
            /*z-index: 1;*/
        }
        li:hover {
            border: 2px solid #333333;
            /*z-index: 1;*/
            position: relative;
        }
    </style>
</head>
<body>
<ul>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li></ul>
<div class="box">

</div>

</body>
</html>